1. Field of the Invention
The present invention relates to a slide fastener having a separable bottom stop assembly at a bottom stopper portion thereof and a method of manufacturing the same.
2. Description of the Prior Art
Conventionally, in a slide fastener in which a coiled or zigzagged fastener element row made of synthetic resin monofilament is attached on a face of a tape by sewing or the like, a core thread is inserted through the fastener element row at a sewed portion of the element row and each element portion of the fastener element row is sewed together with this core thread by sewing yarn. When a separable bottom stop assembly comprising an insert pin, a box pin and a box is attached to a core portion consisting of the core thread and a tape edge portion exposed adjacent a bottom end of the fastener element row attached in the above manner, a tape face side becomes thick because of the existence of the core thread at the core portion. Thus, the thickness of the insert pin and the box pin molded integrally is limited by a section of an element guide groove formed between upper and lower blade plates of a slider, so that the front face side of the fastener tape naturally has to be thickened.
If the volume of resin located on a rear face side decreases when the insert pin and the box pin of synthetic resin are fixed around the core portion at the same time when they are molded, the insert pin and the box pin come to easily peel away from the core portion. As a consequence, the separable bottom stop assembly is broken. To avoid such a damage, according to Japanese Patent Publication No. 56-29524, for example, a tape portion of a core portion is folded stepwise and upward with respect to a fastener tape face so as to fit tightly to a core thread side. After heating the core portion and the periphery of the core portion, the insert pin and the box pin with their thickness substantially equal to the vertical height of the element row are formed around the core portion by injection molding. According to the molding method of this separable bottom stop assembly, a large amount of resin can be also disposed on a rear face side of the core portion. Therefore, the resin does not peel even at the rear face side of the core portion, so durability of the separable bottom stop assembly increases.
However, this method requires a heating apparatus for applying enough heat to the core portion and its periphery in preliminary heat-setting so as to stabilize the folded configuration of the fastener tape. In addition, its thermal history is so large that the core portion and the surrounding portion thereof become brittle. Consequently, the insert pin and the box pin attached around the core portion easily split at their boundary. Additionally, as mentioned above, even if heat-setting is conducted, the configurations of the core portion and its periphery in a cavity may not be maintained upon molding of the separable bottom stop assembly.